1. The Technical Field
The present invention relates to a discharge lamp lighting apparatus that controls lighting of a discharge lamp to be mounted in vehicles or others, and in particular to the discharge lamp lighting apparatus that controls power to be supplied to the discharge lamp in response to a commanded power value supplied from outside the apparatus.
2. Related Art
Currently, a discharge lamp mounted on a vehicle is normally lighted by a light apparatus. Both the discharge lamp and the lighting apparatus are currently provided as different members on a vehicle. The light-emitting characteristic of a discharge lamp to power supplied varies depending on each discharge lamp and the output power from the discharge lamp also varies depending on each discharge lamp lighting apparatus. Hence, when the discharge lamp and the discharge lamp light apparatus, which are mutually separated devises, are electrically connected and operated, the flux of light emitted from the discharge lamp may vary more significantly.
In consideration with this fact, there is known a technique that suppress variations in the foregoing light flux value by adjusting power to be supplied to the discharge lamp. For example, Japanese Patent Laid-open Publication No. 2007-149520 provides a technique to simplify the foregoing adjustment, where the light flux value of a discharge lamp is controlled by providing a power control apparatus with a dimming signal from outside the power control apparatus.
However, even in conducting the foregoing technique that uses the dimming signal supplied externally, which is shown by the foregoing publication, the discharge lamp and the lighting apparatus are separated device by device in a vehicle. In other words, the operating characteristics of both the discharge lamp and the discharge lamp lighting apparatus are not always matched with each other in a one-to-one correspondence. Hence, when the discharge lamp is finally assembled in a vehicle, it is frequent that the value of flux of light varies significantly. In addition, this variation occurs often whenever the discharge lamp and the lighting apparatus are assembled to a vehicle.